A stent delivery system, which is a medical device used to improve a stenosis or occlusion generated in the lumen in vivo, is provided with a dilatable balloon positioned on the outer periphery of the distal portion of a hollow shaft portion, and a stent positioned on the outer periphery of the balloon and having wave-shaped struts that are expanded by the dilatation of the balloon. After reaching a target region (stenosis or occlusion), the stent, which is mounted on the balloon by caulking with its diameter being reduced, is plastically deformed by the dilatation of the balloon and is indwelled in a state of being in close contact with the inner surface of the target region.
The wave-shaped struts of a conventional stent extend in the circumferential direction of the stent and are multiply positioned at intervals in the axial direction of the stent, each of the wave-shaped struts including proximate portions that form portions in the vicinity of an adjacent wave-shaped strut, distant portions that form portions away from the adjacent wave-shaped strut, and straight portions that connect the proximate and distant portions. The proximate portions of adjacent wave-shaped struts are connected by connecting portions.
Since the straight portions of the wave-shaped strut extend in the axial direction of the stent in a state in which the stent is mounted on the balloon, the above-described stent has the problem of being prone to slip along the axial direction of the balloon. The entire stent also has the problem of insufficient flexibility (compliance with the curvature of the lumen in vivo) due to a large difference in stiffness between the wave-shaped struts and the connecting portions.
In view of the improvement in flexibility, extension of the wave-shaped struts in the axial direction of the stent may, for example, reduce the difference in stiffness in the axial direction of the stent (for example, see Japanese PCT National Publication No. 2008-516668, the contents of which are hereby incorporated by reference.)
However, since the proximate portions of adjacent wave-shaped struts in the stent described in Japanese PCT National Publication No. 2008-516668 are directly connected to each other, the proximate portions are hardly deformed even if the stent is expanded by a balloon, and thus the stent may not be expanded well.